After digestion and absorption, food proteins are transported to the tissues of the whole body through blood circulation in the form of amino acids. This source of amino acids is called exogenous amino acids. Body tissue protein in the tissue under the action of the enzyme, has been decomposed into amino acids; the body can synthesize some amino acids (non essential amino acids; amino acids) of these two sources are called endogenous amino acids. There is no difference between exogenous amino acids and endogenous amino acids, which constitute the amino acid metabolic pool (metabolic, pool) of the organism. The amino acid metabolic pool is usually calculated by the total amount of free amino acids. The body does not have a specific tissue and organ to store amino acids. The amino acid metabolic pool actually contains intracellular fluid, intercellular fluid, and amino acids in the blood. The

The main function of amino acids is to synthesize proteins, and also to synthesize peptides and other physiologically active substances containing nitrogen. In addition to outside vitamin (vitamin PP is an exception) in various nitrogen compounds can change by several amino acids, including protein, peptide hormones, amino acid derivatives, melanin, purine, pyrimidine, creatine, amine, or coenzyme cofactor etc.. The

From the amino acid structure, in addition to the side chain of different R group, both alpha amino and carboxyl alpha 13. In amino acid catabolism is actually the amino and carboxyl groups and R metabolism. The main pathways of amino acid catabolism is deaminated to form ammonia and ammonia) and the corresponding alpha keto acids; the other one is the decomposition pathways of amino acid decarboxylation to produce CO2 and amine. Amines can be further decomposed into amines and aldehydes and acids by amine oxidase in the body. Ammonia is toxic to the human body, the ammonia excreted mainly in vivo synthesis of urea, can also synthesize other nitrogenous substances (including non essential amino acid, glutamine, etc.), a small amount of ammonia can be directly excreted in the urine. R group of generating acid can be further decomposed to CO2 oxidation and water, and provide energy, but also by the change of certain metabolic reactions generate sugar or fat stored in the body. Because of the different structures of amino acids, their metabolism also has its own characteristics. The

The role of organs and organs in the metabolism of amino acids is different, among which liver is the most important. The rate of liver protein regeneration is relatively fast, and amino acid metabolism is active. Most of the amino acids are catabolism in liver. Meanwhile, the process of ammonia detoxification is mainly in the liver. The catabolism of branched amino acids occurs mainly in muscle tissues.